Size-controlled CZTS quantum dots (QDs) were synthesized and its application as a potential electron accepting material for polymer-based hybrid solar cell is demonstrated. The CZTS QDs with a size of 2–10 nm were synthesized in a single step by the decomposition of metal dithiocarbamate and characterized by various techniques; like, SEM, TEM, FTIR, XRD, etc. Results reveal that the CZTS QDs synthesized in oleic acid can quench the luminescence of P3HT effectively. Due to the favourable ionization potential and electron affinity values for CZTS with respect to P3HT, the CZTS QDs act as an effective electron acceptor in the hybrid solar cells based on P3HT/CZTS-QD blends which is also revealed by the charge transfer characteristics of P3HT/CZTS blend.